Can you come back to life after being frozen?

Sofia Miettinen

Have you ever wondered if you could come back to life after being frozen? We will take a look at how this could happen and if it has ever been done before…


Cryopreservation is the special name given where cells and tissues are cooled down to very low temperatures to preserve them (make them last longer). This needs to be done carefully as you do not want to cause any damage when cooling things, such as damage caused by ice crystals forming during freezing. Scientists can use carbon dioxide or liquid nitrogen to cool items to temperatures as low as -196 oC; that is more than twice as cold as the lowest temperature ever recorded on earth in Antarctica!


Although no humans have successfully been bought back to life after being frozen, some animals have developed a special feature called “freeze tolerance”. This is where the animal survives winter by freezing its body. Some species of frogs such as the wood frog (Rana sylvatica), turtles such as the box turtle (Terrapene Carolina) and some snakes and lizards have developed this special feature.


Cryopreservation can cause many harmful effects in cells. As the temperatures drop lower and lower:

(1) Water from inside the cells moves outside the cells and causes the cells to become dehydrated.

(2) Water moving outside the cells also causes ice crystals to form outside the cells (extracellular) which can crush the cells.

(3) Ice also forms inside the cell (intracellular) which is very damaging, and as ice crystals grow in freezing water, solutes such as salt do not freeze and end up in high concentrations in the remaining unfrozen water. High concentrations of solutes such as salt can be very damaging because it can draw in lots of water causing the cell to expand unevenly.

Scientists have found that they can prevent this damage caused by freezing by either using slow freezing or flash-freezing techniques. Slow freezing is where things are cooled and frozen slowly and at a steady pace. Scientists like to cool things down by 1 °C every minute and use machines to help them achieve this carefully. Flash-freezing is also called vitrification. Flash-freezing involves using special chemicals called cryoprotectants, which are added before cooling the cells down very quickly. Although these special chemicals are very effective, they can be very harmful and toxic to the cells!


As cryoprotectants are harmful, scientists have been experimenting with replacing blood inside organs with gases such as oxygen to help the organs cool more quickly instead of using cryoprotectants, and this special process is called persufflation.


When a whole body is frozen in the hopes of bringing it back to life in the future, this is called cryonics. The first human body to be frozen which was hoped to be bought back to life in the future was of Dr James Bedford in 1967. He is still frozen today! There are currently four centres in the United States and one in Russia to freeze bodies.


Currently cryopreservation of whole bodies or brains is very damaging, and no human has been bought back to life after being frozen successfully yet. Some parts of the human body have been successfully frozen and unfrozen (thawed) such as blood, eggs (oocytes) and sperm, and many babies have been born from using frozen embryos (human eggs fertilised with sperm) as part of in vitro fertilisation (IVF)!

Egg cell plush toy